The overall objective of the proposed work is to understand the mechanisms by which newly synthesized proteins are unidirectionally translocated across or asymmetrically integrated into distinct cellular membranes. The information for these processes resides in discrete "topogenic" sequences that are either a transient or a permanent part of the protein. The information is decoded by a membrane-associated machinery that is restricted in its localization to distinct cellular membranes. The proposed work attempts to determine the primary structure of the transient topogenic sequences and to identify those portions of the polypeptide chain which contribute permanent topogenic sequences. Furthermore, the proposed work deals with the isolation and characterization of the membrane-associated machinery that is capable of decoding these topogenic sequences.